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Hexadecimal Keypad. Doug Butterworth Email: [email protected] AIM: Epor55 Phone: 814.217.2466. Hardware Description Internal Organization The Circuit in Action Signal Bouncing. Hardware Description:. 16-Button Numeric Keypad Rugged black plastic - PowerPoint PPT Presentation
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Hexadecimal Keypad
• Hardware Description
• Internal Organization
• The Circuit in Action
• Signal Bouncing
Doug Butterworth Email: [email protected] AIM: Epor55 Phone: 814.217.2466
Hardware Description:
16-Button Numeric Keypad • Rugged black plastic • 4 x 4 Matrix Type • 8-position solder pad • Contact rating: 24VDC @ 20mA • Contact resistance: 200 Ohms
max. • Life test: 1,000,000 life cycles
per key • Size: 3.0"L x 2.8"W x 0.6"H• $7.95 from
Links:Product PageTechnical Documentation(pretty under whelming)
Internal Organization
Output organizationOutput pin # SymbolPin 1 Row 2Pin 2 Row 3Pin 3 Col 1Pin 4 Row 4Pin 5 Col 2Pin 6 Col 3Pin 7 Col 4Pin 8 Row 1
When a button is pushed, the associated row and column pin for that button are connected together.
Circuit Diagram
1 2 3 A Row 1
Hex Keypad: The Movie!
QuickTime™ and aCinepak decompressor
are needed to see this picture.
Uses
• Wired into a keypad encoder.(presentation 19 with Anthony Dotterer)
• Xilinx
• Use your imagination…
Signal Bouncing
Background Theory:• Nearly all mechanical switches generate some
bounce.• After switched, they actually open and close
several times before settling down to their new position.
• Can Last as little as a fraction of a millisecond to as long as 50 ms.
• Only very high quality switches generate little or no bounce.
Signal Bouncing
(Simulated by touching a wire to a alligator clip)
Signal Bouncing On the Keypad
(Wow!)
How to prevent:
• Use an RC network to slow either the rising or falling edge of the event.
• Buy a really good switch!